From e1d838cc713f1806edc10a40bb02c9eee922ad24 Mon Sep 17 00:00:00 2001
From: Wenzhi Feng <52550727+thetumbled@users.noreply.github.com>
Date: Tue, 18 Feb 2025 17:59:52 +0800
Subject: [PATCH] [fix][client] fix retry topic with exclusive mode. (#23859)

(cherry picked from commit 5a59ab7768e11db6ed92dada78b398feca9e24fc)
---
 .../pulsar/client/api/RetryTopicTest.java     | 40 +++++++++++++++++++
 .../pulsar/client/impl/ConsumerBase.java      |  8 ++++
 2 files changed, 48 insertions(+)

diff --git a/pulsar-broker/src/test/java/org/apache/pulsar/client/api/RetryTopicTest.java b/pulsar-broker/src/test/java/org/apache/pulsar/client/api/RetryTopicTest.java
index d0e72deb87fc2..2b897760b6f00 100644
--- a/pulsar-broker/src/test/java/org/apache/pulsar/client/api/RetryTopicTest.java
+++ b/pulsar-broker/src/test/java/org/apache/pulsar/client/api/RetryTopicTest.java
@@ -136,6 +136,46 @@ public void testRetryTopic() throws Exception {
         checkConsumer.close();
     }
 
+    /**
+     * Retry topic feature relies on the delay queue feature when consumer produce a delayed message
+     * to the retry topic. The delay queue feature is only supported in shared and key-shared subscription type.
+     * As a result, the subscription type of the retry topic should be shared or key-shared.
+     * @throws Exception
+     */
+    @Test
+    public void testRetryTopicWithExclusiveMode() throws Exception {
+        final String topic = "persistent://my-property/my-ns/retry-topic-exclusive";
+        final int maxRedeliveryCount = 2;
+
+        Consumer<byte[]> consumer = pulsarClient.newConsumer(Schema.BYTES)
+                .topic(topic)
+                .subscriptionName("my-subscription")
+                .subscriptionType(SubscriptionType.Exclusive)
+                .enableRetry(true)
+                .deadLetterPolicy(DeadLetterPolicy.builder().maxRedeliverCount(maxRedeliveryCount).build())
+                .receiverQueueSize(100)
+                .subscriptionInitialPosition(SubscriptionInitialPosition.Earliest)
+                .subscribe();
+
+        Producer<byte[]> producer = pulsarClient.newProducer(Schema.BYTES)
+                .topic(topic)
+                .create();
+
+        producer.send("Hello Pulsar".getBytes());
+        producer.close();
+
+        // receive message and set delay to 5 seconds
+        Message<byte[]> message = consumer.receive();
+        long timestamp = System.currentTimeMillis();
+        consumer.reconsumeLater(message, 4, TimeUnit.SECONDS);
+
+        // receive message and check the delay is at least 4 seconds
+        consumer.receive();
+        long delay = System.currentTimeMillis() - timestamp;
+        assertTrue(delay >= 2000);
+        consumer.close();
+    }
+
     @Data
     public static class Foo {
         @Nullable
diff --git a/pulsar-client/src/main/java/org/apache/pulsar/client/impl/ConsumerBase.java b/pulsar-client/src/main/java/org/apache/pulsar/client/impl/ConsumerBase.java
index 1ad8c6d28f1d7..27e2216e58949 100644
--- a/pulsar-client/src/main/java/org/apache/pulsar/client/impl/ConsumerBase.java
+++ b/pulsar-client/src/main/java/org/apache/pulsar/client/impl/ConsumerBase.java
@@ -48,6 +48,7 @@
 import org.apache.pulsar.client.api.Consumer;
 import org.apache.pulsar.client.api.ConsumerBuilder;
 import org.apache.pulsar.client.api.ConsumerEventListener;
+import org.apache.pulsar.client.api.DeadLetterPolicy;
 import org.apache.pulsar.client.api.Message;
 import org.apache.pulsar.client.api.MessageId;
 import org.apache.pulsar.client.api.MessageIdAdv;
@@ -792,6 +793,13 @@ private boolean isCumulativeAcknowledgementAllowed(SubscriptionType type) {
     }
 
     protected SubType getSubType() {
+        // For retry topic, we always use Shared subscription
+        // Because we will produce delayed messages to retry topic.
+        DeadLetterPolicy deadLetterPolicy = conf.getDeadLetterPolicy();
+        if (deadLetterPolicy != null && topic.equals(deadLetterPolicy.getRetryLetterTopic())) {
+            return SubType.Shared;
+        }
+
         SubscriptionType type = conf.getSubscriptionType();
         switch (type) {
         case Exclusive: